Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$135.81	6.141%	$144.1501	$144.15	$144.15	$144.20
Purchase #2	$203.94	7.501%	$219.2375	$219.24	$219.25	$219.20
Purchase #3	$134.64	13.403%	$152.6858	$152.69	$152.70	$152.70
Purchase #4	$174.43	8.742%	$189.6787	$189.68	$189.70	$189.70
Purchase #5	$127.89	9.841%	$140.4757	$140.48	$140.50	$140.50
Purchase #6	$113.92	9.703%	$124.9737	$124.97	$124.95	$125.00
Purchase #7	$141.72	7.344%	$152.1279	$152.13	$152.15	$152.10
7 purchase totals =	$1,032.35		$1,123.3294	$1,123.34	$1,123.40	$1,123.40